rustc_macros/

lib.rs

// tidy-alphabetical-start
#![allow(
    rustc::default_hash_types,
    reason = "we like performance but can't use `rustc_data_structures`"
)]
#![deny(
    rustc::potential_query_instability,
    reason = "macros shall produce deterministic output/errors"
)]
#![feature(never_type)]
#![feature(proc_macro_diagnostic)]
#![feature(proc_macro_tracked_env)]
// tidy-alphabetical-end

use proc_macro::TokenStream;
use synstructure::decl_derive;

mod current_version;
mod diagnostics;
mod extension;
mod lift;
mod print_attribute;
mod query;
mod serialize;
mod stable_hash;
mod symbols;
mod type_foldable;
mod type_visitable;
mod visitable;

// Reads the rust version (e.g. "1.75.0") from the CFG_RELEASE env var and
// produces a `RustcVersion` literal containing that version (e.g.
// `RustcVersion { major: 1, minor: 75, patch: 0 }`).
#[proc_macro]
pub fn current_rustc_version(input: TokenStream) -> TokenStream {
    current_version::current_version(input)
}

#[proc_macro]
pub fn rustc_queries(input: TokenStream) -> TokenStream {
    query::rustc_queries(input)
}

#[proc_macro]
pub fn symbols(input: TokenStream) -> TokenStream {
    symbols::symbols(input.into()).into()
}

/// Derive an extension trait for a given impl block. The trait name
/// goes into the parenthesized args of the macro, for greppability.
/// For example:
/// ```
/// use rustc_macros::extension;
/// #[extension(pub trait Foo)]
/// impl i32 { fn hello() {} }
/// ```
///
/// expands to:
/// ```
/// pub trait Foo { fn hello(); }
/// impl Foo for i32 { fn hello() {} }
/// ```
#[proc_macro_attribute]
pub fn extension(attr: TokenStream, input: TokenStream) -> TokenStream {
    extension::extension(attr, input)
}

decl_derive!(
    [StableHash, attributes(stable_hash)] => stable_hash::stable_hash_derive
);
decl_derive!(
    [StableHash_NoContext, attributes(stable_hash)] => stable_hash::stable_hash_no_context_derive
);

// Encoding and Decoding derives
decl_derive!([Decodable_NoContext] =>
    /// See docs on derive [`Decodable`].
    ///
    /// Derives `Decodable<D> for T where D: Decoder`.
    serialize::decodable_nocontext_derive
);
decl_derive!([Encodable_NoContext] => serialize::encodable_nocontext_derive);
decl_derive!([Decodable] =>
    /// Derives `Decodable<D> for T where D: SpanDecoder`
    ///
    /// # Deriving decoding traits
    ///
    /// > Some shared docs about decoding traits, since this is likely the first trait you find
    ///
    /// The difference between these derives can be subtle!
    /// At a high level, there's the `T: Decodable<D>` trait that says some type `T`
    /// can be decoded using a decoder `D`. There are various decoders!
    /// The different derives place different *trait* bounds on this type `D`.
    ///
    /// Even though this derive, based on its name, seems like the most vanilla one,
    /// it actually places a pretty strict bound on `D`: `SpanDecoder`.
    /// It means that types that derive this can contain spans, among other things,
    /// and still be decoded. The reason this is hard is that at least in metadata,
    /// spans can only be decoded later, once some information from the header
    /// is already decoded to properly deal with spans.
    ///
    /// The hierarchy is roughly:
    ///
    /// - derive [`Decodable_NoContext`] is the most relaxed bounds that could be placed on `D`,
    ///   and is only really suited for structs and enums containing primitive types.
    /// - derive [`BlobDecodable`] may be a better default, than deriving `Decodable`:
    ///   it places fewer requirements on `D`, while still allowing some complex types to be decoded.
    /// - derive [`LazyDecodable`]: Only for types containing `Lazy{Array,Table,Value}`.
    /// - derive [`Decodable`] for structures containing spans. Requires `D: SpanDecoder`
    /// - derive [`TyDecodable`] for types that require access to the `TyCtxt` while decoding.
    ///   For example: arena allocated types.
    serialize::decodable_derive
);
decl_derive!([Encodable] => serialize::encodable_derive);
decl_derive!([TyDecodable] =>
    /// See docs on derive [`Decodable`].
    ///
    /// Derives `Decodable<D> for T where D: TyDecoder`.
    serialize::type_decodable_derive
);
decl_derive!([TyEncodable] => serialize::type_encodable_derive);
decl_derive!([LazyDecodable] =>
    /// See docs on derive [`Decodable`].
    ///
    /// Derives `Decodable<D> for T where D: LazyDecoder`.
    /// This constrains the decoder to be specifically the decoder that can decode
    /// `LazyArray`s, `LazyValue`s amd `LazyTable`s in metadata.
    /// Therefore, we only need this on things containing LazyArray really.
    ///
    /// Most decodable derives mirror an encodable derive.
    /// [`LazyDecodable`] and [`BlobDecodable`] together roughly mirror [`MetadataEncodable`]
    serialize::lazy_decodable_derive
);
decl_derive!([BlobDecodable] =>
    /// See docs on derive [`Decodable`].
    ///
    /// Derives `Decodable<D> for T where D: BlobDecoder`.
    ///
    /// Most decodable derives mirror an encodable derive.
    /// [`LazyDecodable`] and [`BlobDecodable`] together roughly mirror [`MetadataEncodable`]
    serialize::blob_decodable_derive
);
decl_derive!([MetadataEncodable] =>
    /// Most encodable derives mirror a decodable derive.
    /// [`MetadataEncodable`] is roughly mirrored by the combination of [`LazyDecodable`] and [`BlobDecodable`]
    serialize::meta_encodable_derive
);

decl_derive!(
    [TypeFoldable, attributes(type_foldable)] =>
    /// Derives `TypeFoldable` for the annotated `struct` or `enum` (`union` is not supported).
    ///
    /// The fold will produce a value of the same struct or enum variant as the input, with
    /// each field respectively folded using the `TypeFoldable` implementation for its type.
    /// However, if a field of a struct or an enum variant is annotated with
    /// `#[type_foldable(identity)]` then that field will retain its incumbent value (and its
    /// type is not required to implement `TypeFoldable`).
    type_foldable::type_foldable_derive
);
decl_derive!(
    [TypeVisitable, attributes(type_visitable)] =>
    /// Derives `TypeVisitable` for the annotated `struct` or `enum` (`union` is not supported).
    ///
    /// Each field of the struct or enum variant will be visited in definition order, using the
    /// `TypeVisitable` implementation for its type. However, if a field of a struct or an enum
    /// variant is annotated with `#[type_visitable(ignore)]` then that field will not be
    /// visited (and its type is not required to implement `TypeVisitable`).
    type_visitable::type_visitable_derive
);
decl_derive!(
    [Walkable, attributes(visitable)] =>
    /// Derives `Walkable` for the annotated `struct` or `enum` (`union` is not supported).
    ///
    /// Each field of the struct or enum variant will be visited in definition order, using the
    /// `Walkable` implementation for its type. However, if a field of a struct or an enum
    /// variant is annotated with `#[visitable(ignore)]` then that field will not be
    /// visited (and its type is not required to implement `Walkable`).
    visitable::visitable_derive
);
decl_derive!([Lift, attributes(lift)] => lift::lift_derive);
decl_derive!(
    [Diagnostic, attributes(
        // struct and field attributes
        diag,
        help,
        help_once,
        note,
        note_once,
        warning,
        // field attributes
        primary_span,
        label,
        subdiagnostic,
        suggestion,
        suggestion_short,
        suggestion_hidden,
        suggestion_verbose)] =>
        #[doc = "See <https://rustc-dev-guide.rust-lang.org/diagnostics/diagnostic-structs.html#derivediagnostic>"]
        diagnostics::diagnostic_derive
);
decl_derive!(
    [Subdiagnostic, attributes(
        // struct/variant attributes
        label,
        help,
        help_once,
        note,
        note_once,
        warning,
        subdiagnostic,
        suggestion,
        suggestion_short,
        suggestion_hidden,
        suggestion_verbose,
        multipart_suggestion,
        multipart_suggestion_short,
        multipart_suggestion_hidden,
        // field attributes
        primary_span,
        suggestion_part,
        applicability)] => diagnostics::subdiagnostic_derive
);

/// This macro creates a translatable `DiagMessage` from a fluent format string.
/// It should be used in places where a translatable message is needed, but struct diagnostics are undesired.
///
/// This macro statically checks that the message is valid Fluent, but not that variables in the Fluent message actually exist.
#[proc_macro]
pub fn msg(input: TokenStream) -> TokenStream {
    diagnostics::msg_macro(input)
}

decl_derive! {
    [PrintAttribute] =>
    /// Derives `PrintAttribute` for `AttributeKind`.
    /// This macro is pretty specific to `rustc_hir::attrs` and likely not that useful in
    /// other places. It's deriving something close to `Debug` without printing some extraneous
    /// things like spans.
    print_attribute::print_attribute
}